The invention relates to the field of converters such as inverters, for example those used in uninterruptible power supplies, in particular in high-power uninterruptible power supplies, i.e. with a power generally comprised between about 100 and 500 kVA.
The invention more particularly concerns a unidirectional converter device designed to supply a substantially DC output voltage on an output line, said device being equipped with at least one switching unit comprising:                a power supply input on which a generally variable input voltage is applied,        rectifier means connected to said power supply input to supply the output voltage,        switching means connected to said power supply input to obtain main turn-on or main turn-off of an input current so that, when main turn-off occurs, said input current is diverted to said rectifier means,        control means of said switching means, and        a switching aid circuit arranged between the power supply input and the output line to establish a switching voltage substantially equal to zero, before main turn-on, said switching aid circuit comprising inductive means, input current branch-off means, and power storage means parallel-connected on the switching means to establish a resonance of said current in the inductive means before main turn-on.        